Clearing the Air in the Smokies

A fine mist hugs the earth, creating an ombre of green to gray to blue. The indigo ripples of land continue thereafter, undulating until they blend into the horizon. The sky swells above the mist in a crisp cobalt. Or so I imagined: I had seen the Smoky Mountains in advertisements and travel photography — on reprints on shirts, mugs and socks long before I stepped foot into Great Smoky Mountains National Park.

But as I ventured into the national park for the first time in my late 20s in 2018, panting up a half-mile paved path to reach the highest point at Clingmans Dome, I did not see the view I imagined. From my 6,643-foot perch on a concrete UFO-like deck, I stared into a thick, dark cloud. We were in a haze. “Guess that’s why they call it the Smoky Mountains,” I said to my partner.

Yet what I experienced wasn’t the “smoke” that gave the Smoky Mountains their name. Since the 1960s, people began to take note of a different kind of haze infiltrating the park — one fed by the fossil-fuel-burning industry, motor vehicles and the airborne side effects of agriculture and development. In the park, ground-level ozone and fine particulate matter threaten human health.

Sensitive plants like black cherry trees and cut-leaf coneflowers have shown signs of damage from ground-level ozone and have stopped thriving. Nitrogen and sulfur pollution have settled into the soil and have seeped into surrounding streams, diminishing water quality and harming aquatic species like brook trout.

The visitors who venture to the park expect clean, clear air — and the National Park Service dedicates itself to living up to those expectations. The trouble with air pollution, though, is that it travels, often far and wide. The air in Maine’s Acadia National Park, for example, suffers when harmful airborne particulates and emissions head over from the Midwest and surrounding Northeast states.

The great majority of the air pollution in the Smokies likewise comes from outside the park, in the Midwest and Northeast, as well as closer to home: the greater Southeastern region. Even so, the National Park Service can’t solve this problem alone.

To address the air affecting the plants and creatures who call Great Smoky Mountains National Park home and the visitors who come to gaze out on its majesty and wonder, the Park Service has turned to community and partnerships.

Momentum to improve air quality started in the 1970s at the federal level, when Congress first passed the Clean Air Act and then its amendments, including the Class I visibility goals for 156 national parks and wilderness areas. After these goals were set to remedy existing air pollution problems and prevent future deterioration, the U.S. Environmental Protection Agency established Regional Haze Rule regulations in 1999 that offer more protections for large natural places like the Smoky Mountains.

With these federal regulations in place, the park developed an extensive air monitoring program in the early 1980s. Park staff set up monitoring stations in a handful of strategic locations and elevations throughout the park to get regular readings on the air issues they faced. With data and computer modeling, park experts could identify the pollutants of concern and where emissions were coming from. And with that, they could start addressing the problem from the source.

Jim Renfro is one of those experts. He has served as the air quality specialist in Great Smoky Mountains National Park for the last 38 years, nearly since the air monitoring program started.

“In the ’80s and even into the late ’90s, air quality was poor and wasn’t getting better. It was actually worsening. We had high levels of acid rain, haziness, high ozone pollution and particulate matter. Some of the pollutants that affect people’s health were high enough that we were exceeding human health standards on most summer days,” Renfro said. “We didn’t see much improvement, really, until there was a focus on the eastern United States.”

Almost all our national parks suffer from some degree of air pollution, as evidenced by NPCA’s 2024 “Polluted Parks” report, but Great Smoky Mountains National Park faces particular challenges. The park experiences high rainfall and humidity that increase pollutant deposition and haze. As in other parts of the country, intense sunlight, heat and high air pressure in the Southeast stir up dangerous chemical reactions from the pollutants drifting into the park. On top of that, the Smoky Mountains trap air currents like big natural buffers stacked one behind another.

So when the surrounding 70-plus coal-powered plants and other pollution-producing facilities, as identified by NPCA’s interactive data map, spew sulfur dioxide and nitrogen oxide emissions that threaten human breathing and reduce views, the hazy air gathers in the Smoky Mountains like another eager (albeit unwelcome) visitor.

Yet the fact that pollution sources were regional turned out to be an advantage in some ways. In the 1990s and 2000s, Renfro traveled throughout the Southern Appalachian region, spreading the word on their air quality issues and what industry and people could do about it. With his long-term datasets, he advised local, state, Tribal and federal EPA professionals creating regulations and enforcing current clean air standards to protect public health and park resources. He also informed and inspired the public to take action at home to reduce their impact on air quality. Renfro’s team helped inform and shape the 2002 North Carolina Clean Smokestacks Act that reduced power plant emissions in the area and the 2005 Clean Air Interstate Rule (CAIR) that limited sulfur and nitrogen emissions from large units like boilers and turbines used to generate electricity.

“We’re a good barometer because we’re right in the middle of the Southeast. If we’re improving — and we are — I would bet that the region is improving. Likewise, if the region improves, we probably do, too,” Renfro said.

The decades-long data Renfro has collected confirms the cumulative success of that collaboration, a win-win for the region and the park. An EPA graph of sulfur dioxide and nitrogen oxide emissions from 1990 to 2022 shows a decline in the two types of emissions.

“In the last 20 to 25 years, the air quality has gotten better because of a lot of reductions in millions of tons of sulfur dioxide and nitrogen oxides that have made the air better, cleaner, clearer. There’s less acid rain, less particulates, less haze, less unhealthy days,” Renfro said. “So that’s a really remarkable story where we turned it around by using our data and working together.”

Renfro stresses the park still has a way to go to reach the EPA’s goal of returning Class I U.S. national parks and wilderness areas to their natural visibility conditions by 2064. Nitrogen oxides and sulfur dioxide emitted from burning fossil fuels, for example, continue to create pollutants of concern at the park’s monitoring stations. Visitors will still sometimes see unnatural haze as they gaze out into the distance, limiting their views that should stretch about 100 miles into the distance to 46 miles or less. Renfro says visibility used to average nine miles on the haziest days before clean air improvements.

Visitors may still notice high ozone warnings posted throughout the park after nitrogen oxides react with sunlight and the natural organic chemicals in the area to form ozone. These unhealthy ozone days are occurring less often and remain a concern. But experts like Renfro and countless others — including NPCA — have their eyes and tools pointed at these problems, and they’re committed to keeping up the momentum. This includes continuing to support the EPA’s Regional Haze Rule and developing new technological solutions and programs to keep reducing pollutants to prevent adverse impacts at the park.

“The modeling projected out to the end of this decade shows that we’re going to continue to get better — that haziness is going to go down,” Renfro said.

Less unnatural haziness will give way to the quintessential blue mist the Smoky Mountains are named for. This comes from natural volatile organic compounds (VOCs). The millions of surrounding trees and foliage within the park seep moisture that gathers into a vaporous fog. The risen VOC molecules paint the mountains a blue hue by scattering the sunlight.

On clear days during a recent park visit, I spotted the difference between the pollution and natural haze. The view was like a blue-filmed windshield scrubbed clean of years of gravel dust. I arrived at Cades Cove and gazed at the blazing blue mountains enveloping me in the 2,000-acre valley. I saw what the Cherokee people saw as they deemed the area Shaconage: “land of the blue smoke.”

I looked out into the distance at the miles of the protected national park that we share. I inhaled the air, and with my senses alone I could not say where the level of chemicals or particulate matter stood in that moment. But from my vantage point now, I detect strong notes of hope.